Designers of cargo containers have long faced many related challenges in the design of container sidewalls. First, the structural integrity of the overall container depends on the rigidity and strength of the sidewalls. Second, the sidewalls are optimally light in weight to reduce the transportation costs for the overall container.
Third, government regulations or industry standards often limit the exterior dimensions of cargo containers. Thus, to maximize the capacity of the container, designers seek to minimize the width of the sidewalls without compromising the structural integrity of the container.
Fourth, because cargo containers are repeatedly loaded and unloaded, the interior walls of the container must be resistant to the repeated impact of vehicles and implements used to load and unload the container. Containers must optimally be free of protrusions and snag points that could impede loading and unloading. Fifth, means for securing and dividing cargo within a container are often desirable, and may be provided by incorporating logistics slots in the sidewalls of the container. Sixth, even resilient sidewalls may become damaged with extended use and require replacement or repair, Seventh, installing bolts or rivets commonly used in assembling sidewalls increases the container construction time, sidewall thickness, and the cost of the container. Eighth, various thicknesses of panels are used in container construction based on the desired characteristics of the container. Connectors between panels must be adaptable to these various thicknesses. Other considerations, including the cost and availability of the sidewall components and the ease of manufacturing, are also important.
These challenges are particularly acute in the design and construction of sidewalls for over-the-road trailers. Structural integrity for trailers is of course essential to the safe transportation of goods and materials on public highways. This structural integrity has conventionally been provided by either a “sheet and post” or a structural panel sidewall construction.
In sheet and post sidewall construction, vertical posts are used to provide the primary structural integrity for the trailer. Such posts are typically formed by bending or roll forming galvanized steel or extruding aluminum into non-linear shape, thus providing rigidity and strength for the post. Relatively thin and easily replaceable sidewall sheets, typically made of plywood or plastic, are attached to the vertical posts in the interior of the trailer and a protective outer skin is attached to the exterior of the trailer. A protective metal, wood, or plastic liner may also be provided at the base of the interior sidewall to protect the sheets and posts from being damaged or pierced by vehicles loading and unloading the trailer. This sheet and post design offers certain advantages, including high structural strength attributable to the vertical posts, lower cost and ease of manufacturing, among others. Also, although the thin interior sheets are susceptible to damage, these sheets are relatively inexpensive and easy to replace. Conventional sheet and post designs, however, suffer from a key disadvantage, namely, the thickness of the posts required to provide structural integrity for the trailer.
Structural panel sidewalls have also been used in the construction of over-the-road trailers to address many of the challenges related to cargo containers. In particular, because of the strength and rigidity of the structural panels, sidewall thickness can generally be reduced as compared to conventional sheet and post designs. The structural panels are typically joined at their edges with vertical splicer plates on the inside and outside of the trailer, as shown in U.S. Pat. No. 4,904,017 (FIG. 9) issued to Ehrlich, U.S. Pat. No. 5,860,693 (FIG. 2) issued to Ehrlich and U.S. Pat. No. 6,450,564 (FIG. 3) and U.S. Pat. No. 6,578,902 (FIGS. 4 and 5) issued to Sill. The structural panels may also be joined with vertical posts on the inside and outside of the trailer, as disclosed in the applicant's U.S. Pat. No. 7,152,912 and incorporated herein by reference. These vertical posts are typically provided with logistics slots for securing and dividing cargo within the trailer.
Structural panels are often composite panels made of a core plastic material and an outer skin of aluminum or steel. The metal skin of the panels is resistant to damage when the cargo is loaded and unloaded, and because of the strength and rigidity of the composite panels, trailer sidewall thickness can generally be reduced as compared to sheet and post designs. Although lighter in weight than solid aluminum panels, composite panels are typically more expensive than the materials used in conventional sheet and post designs. Additionally, structural panel sidewalls are difficult and expensive to replace if a single panel becomes damaged.
The use of rivets to connect structural panels to posts or plates often increases the thickness of the sidewall, and also increases the number of snag points inside the container. Additionally, the use of rivets increases the number of parts used in constructing the container which can increase the cost and time to manufacture a cargo container.
Some of the advantages of a rivetless cargo container sidewall that combines the thin cross-section of structural panel sidewalls with the easily replaceable interior panels of a sheet and post configuration have been recognized.
U.S. Pat. No. 5,584,527 issued to Sitter discloses a “plate-type” trailer with a rivetless and boltless sidewall construction. This configuration includes corrugated panels and “seam extrusion members” that connect the corrugated panels. The corrugation of the paneling in the '527 patent decreases the total available space inside the trailer, and the connectors make panel replacement difficult. Thus, the need remains for a rivetless and boltless sidewall construction that allows for easy replacement of damaged panels.
U.S. Pat. No. 5,403,062 issued to Sjostedt discloses a “panel joint” trailer with a rivetless and boltless sidewall construction. This configuration includes modular panels with integral protrusions, tapered end sections, and adhesive to join the tapered end section of one panel to the integral protrusion section of another panel. The panels disclosed by the '062 patent are highly interconnected, and therefore not easily replaceable.
U.S. Pat. Nos. 5,860,693, 6,220,651, 6,412,854, 6,986,546, and 7,069,702 issued to Ehrlich disclose a structural panel joint configuration. This configuration includes a pair of panels and two metal plates connected by rivets. However, the panels are not easily replaceable due to the use of rivets.
Accordingly, an object of the present invention is to provide a sidewall construction for a cargo container that is lightweight yet rigid and strong.
A further object of the present invention is to provide a cargo container with thin sidewalls to maximize the capacity of the container.
Another object of the present invention is to provide a sidewall construction that does not require the use of bolts or rivets.
Yet another object of the present invention is to provide a cargo container with interior walls resistant to the impact of vehicles and implements used to load and unload the container, and to provide a cargo container with minimal protrusions and snag points that could impede the loading or unloading of the container.
An additional object of the present invention is to provide a cargo container sidewall with panels that can be easily removed and replaced in the event they become damaged.
A still further object of the present invention is to provide a cargo container with interior logistics slots in the container sidewalls for securing cargo.
Still another object of the present invention is to provide a highly rigid, yet thin, two piece connector for use in a structural panel sidewall construction.
Finally, an object of the present invention is to provide a cargo container sidewall configuration that that is economical to manufacture and refined in appearance.